Hives are raised red welts of various size on the surface of the skin, often itchy , which come and go.

Alternative Names

Urticaria

Causes, incidence, and risk factors

Hives are very common, especially in people who have experienced other allergic reactions , including hay fever and angioedema . The welts occur on the surface of the skin, usually in batches. Release of histamine and other chemicals into the bloodstream, associated with the allergic response , causes the itching , localized swelling, and other symptoms. Many substances, called allergens, can trigger an allergic response resulting in hives. Common allergens include:

Medications

Foods (such as berries,

shellfish , fish, nuts, eggs, milk, and others)

Pollen

Animal dander (especially cats)

Insect bites

Hives may also develop after infections or illness (including

autoimmune diseases , leukemia , and others). There seems to be a hereditary tendency toward the development of hives. Some less common causes of hives include:

Cold urticaria

Lupus erythematosus

(

SLE )

Echinococcus

infection (dog tapeworm)

Hereditary angioedema

Mononucleosis

Hepatitis

Mastocytosis

Signs and tests

The diagnosis is primarily based on the appearance of the skin, and is confirmed by a history of exposure to an allergen . Occasionally, skin or blood tests may be performed.

Treatment

Hives in the throat may obstruct the airway, so any swelling in the throat or difficulty breathing with hives are emergency symptoms. Call your local emergency medical services or visit the emergency room immediately. Treatment may not be needed if hives are mild, and they may disappear spontaneously. Antihistamines, adrenaline (epinephrine), corticosteroids (prednisone), sedatives, or tranquilizers may reduce the inflammation, itching , and swelling. Self care: Cool compresses or soaks to the area may reduce swelling and pain. Avoid irritation of the area, and don't wear tight clothing (which may trigger a new outbreak). Avoid known allergens to prevent recurrence of hives.

Expectations (prognosis)

Hives may be uncomfortable, but they generally are harmless and disappear on their own. In most cases, the exact cause of hives can not be identified.

Complications

Anaphylaxis

Life-threatening

airway obstruction , if swelling occurs in the throat

Calling your health care provider

Call your health care provider if urticaria is severe and does not respond to treatment. Call your health care provider or go to the emergency room if there is difficulty breathing , severe wheezing , or if fainting occurs.

Prevention

Avoid exposure to substances that are a known

allergen for you.

Take only prescribed medications.

Avoid hot baths or showers after an episode of urticaria to prevent recurrence.